1. Field of the Invention
This invention generally relates to a reciprocating tool. This invention specifically relates to a power tool for reciprocating a cutting blade. Examples of the power tool are a jigsaw and a saber saw.
2. Description of the Related Art
U.S. Pat. No. 4,031,763 discloses a reciprocating power tool in which the length of the stroke of the tool member can be adjusted. The tool in U.S. Pat. No. 4,031,763 includes a screw adjustment member having a hand knob. The screw adjustment member is mounted in the tool housing. When the screw adjustment member is rotated, it changes the position of one end of a first lever. The other end of the first lever bears against a rotating member which is mounted on the power output shaft of the tool. As the rotating member is adjusted, it causes a second lever to rotate and thereby changes the position of the arm of the reciprocating mechanism with respect to the shaft of the power drive means. Thus, as the knob on the screw adjustment member is rotated, the swing arm length of the eccentric driven by the power source may be varied.
U.S. Pat. No. 5,134,777 discloses an adjustable stroke reciprocating mechanism for a power tool. According to U.S. Pat. No. 5,134,777, the ram of the reciprocating saw is driven by a scotch yoke mechanism. A planetary gear system consisting of a ring gear and an idler gear imparts an elliptical or linear path of movement to the pin forming part of the scotch yoke mechanism. The ring gear may be adjustably positioned for changing its relationship relative to the idler gear, thereby varying the orientation of the elliptical or linear path of movement of the drive pin for varying the stroke of reciprocation of the ram which is connected to the saw blade holder. Actuation of the ring gear to its desired position automatically causes the foot plate of the saw to be located in its desired position for the selected stroke of movement. The idler gear has an eccentric pin which fits into a slot in the ram. As the ring gear is rotated, an angular position of the idler gear changes so that the stroke of reciprocation of the ram varies.
U.S. Pat. No. 5,581,896 discloses a reciprocating action tool having a stroke adjusting mechanism. The tool in U.S. Pat. No. 5,581,896 includes a disc rotatably received in a housing, and a shaft slidably engaged in the upper portion of the housing. The disc includes a bolt rotatably engaged in a groove and a slide threadedly engaged with the bolt. The slide includes a stud for rotatably supporting a follower which is slidably engaged with the shaft. The slide is moved longitudinally along the groove so as to adjust a moving stroke and a moving speed of the shaft. The shaft is moved quickly for driving a cutting tool and is moved slowly for moving a saw blade or a file.
Japanese published unexamined patent application 59-176001 discloses a jigsaw including a reciprocation stroke varying mechanism via which a power source and a saw blade are connected. The reciprocation stroke varying mechanism includes a cam rod, and a drive shoe with which the cam rod is in engagement. The inclination angle of the drive shoe is variable.
It is an object of this invention to provide an improved reciprocating tool.
A first aspect of this invention provides a reciprocating tool comprising a rotatable drive gear; a pin connected to the drive gear and being eccentric with respect to an axis of rotation of the drive gear; a plunger extending perpendicular to the pin and being movable upward and downward; a connector engaging the plunger and the pin; a cam provided with the pin at an eccentric position; a cam holding member holding the cam at an eccentric position and being connected to the drive gear for rotation responsive to rotation of the drive gear; a first engagement portion provided on the cam; a second engagement portion provided on the cam holding member and being engageable with the first engagement portion; first means for cancelling engagement between the first engagement portion and the second engagement portion to allow rotation of the cam relative to the cam holding member; and second means for establishing engagement between the first engagement portion and the second engagement portion while holding the cam at an angular position which occurs as a result of the rotation of the cam.
A second aspect of this invention is based on the first aspect thereof, and provides a reciprocating tool wherein the cam holding member having an eccentric recess accommodating at least part of the cam, and the cam holding member and the drive gear are integral with each other.
A third aspect of this invention is based on the first aspect thereof, and provides a reciprocating tool wherein the first engagement portion includes a projection, and the second engagement portion includes a recess into which the projection is movable.
A fourth aspect of this invention is based on the first aspect thereof, and provides a reciprocating tool wherein the first engagement portion includes a plurality of first sub engagement portions spaced at equal angular intervals, and the second engagement portion includes a plurality of second sub engagement portions spaced at equal angular intervals and being engageable with the first sub engagement portions respectively.
A fifth aspect of this invention is based on the first aspect thereof, and provides a reciprocating tool further comprising a weight provided on the cam and having a mass substantially equal to that of the pin, and a position of the weight and a position of the pin are symmetrical with respect to a central axis of the cam. A sixth aspect of this invention is based on the first aspect thereof, and provides a reciprocating tool further comprising a counter rack substantially equal in mass to the plunger, and means for moving the counter rack in a direction opposite to a direction of movement of the plunger.
A seventh aspect of this invention is based on the first aspect thereof, and provides a reciprocating tool wherein the drive gear includes a normal-speed gear and a high-speed gear, and further comprising means for selectively connecting the cam holding member with one of the normal-speed gear and the high-speed gear.
An eighth aspect of this invention is based on the seventh aspect thereof, and provides a reciprocating tool wherein the plunger reciprocates as the drive gear rotates in cases where the first engagement portion and the second engagement portion are in engagement with each other, and a stroke of the plunger depends on an angular position of the cam relative to the cam holding member, and wherein the cam holding member is connected with the high-speed gear when the stroke of the plunger is set to a first value, and is connected with the normal-speed gear when the stroke of the plunger is set to a second value greater than the first value.
A ninth aspect of this invention provides a reciprocating tool comprising a drive member rotatable about its axis; a cam eccentrically connected to the drive member for rotation responsive to rotation of the drive member; a plunger; a cam follower fixed to the plunger and engaging the cam for reciprocating the plunger as the cam rotates, wherein a stroke of reciprocation of the plunger depends on an angular position of the cam relative to the drive member; means for changing the angular position of the cam relative to the drive member to vary the stroke of reciprocation of the plunger; and a bearing provided between the cam and the cam follower.
A tenth aspect of this invention is based on the ninth aspect thereof, and provides a reciprocating tool wherein the cam has a pin at its eccentric position, and the cam follower has a groove into which the pin extends, and wherein the bearing is located between the cam follower and the pin in the groove.